The present invention relates to a longwall mining machine of the type having a pivot arm which supports a cutter drum for rotation about an axis for working a mine face. A cowl or clearing shield is positioned at a desired location about the periphery of the cutter drum. In a mining machine of this type, the rotating cutter drum cuts the material being mined and is provided with spirals which assist in loading the mine material onto a face conveyor. The loading efficiency is improved with the use of the cowl comprising an arcuate plow which follows behind the cutter drum and which can be pivoted from one side of the drum to the other, depending upon the direction of movement of the mining machine.
In West German Offenlegungsschrift No. 26 48 881, there is disclosed a system for pivoting a cowl of this type in which the cowl is mounted for pivotal movement about the rotational axis of the cutter drum. A hydraulic motor, used to effect pivotal movement, engages a gear element situated centrally with respect to the rotational axis of the cutter drum and is disposed within the plane of the pivoting gear element. A holder for the cowl is connected to the pivoting gear element which rides on a relatively narrow annulus. Since the cowl extends over the entire length of the cutter drum but is borne only at one side of the drum by the narrow annulus, both the pivoting gear and the annulus carrying the same experience severe stresses because of their narrowness. These stresses, caused by the weight of the cowl, and also because of its single-ended overhung or cantilever mounting, result in bending moments, particularly in the case of large diameter cutter drums.
Another arrangement for pivoting a cowl of the type described above is shown in copending application Ser. No. 44,790, filed May 31, 1979, now U.S. Pat. No. 4,251,112. In this case, as in the German publication described above, the ring on which the cowl is carried rotates on a relatively narrow annulus which is subject to substantial stress.